13,599 research outputs found
Structures in granitic bathyliths and associated foldbelts in relation to mineral resources
There are no author-identified significant results in this report
Monte Carlo Simulation of Lyman Alpha Scattering and Application to Damped Lyman Alpha Systems
A Monte Carlo code to solve the transfer of Lyman alpha (Lya) photons is
developed, which can predict the Lya image and two-dimensional Lya spectra of a
hydrogen cloud with any given geometry, Lya emissivity, neutral hydrogen
density distribution, and bulk velocity field. We apply the code to several
simple cases of a uniform cloud to show how the Lya image and emitted line
spectrum are affected by the column density, internal velocity gradients, and
emissivity distribution. We then apply the code to two models for damped Lya
absorption systems: a spherical, static, isothermal cloud, and a flattened,
axially symmetric, rotating cloud. If the emission is due to fluorescence of
the external background radiation, the Lya image should have a core
corresponding to the region where hydrogen is self-shielded. The emission line
profile has the characteristic double peak with a deep central trough. We show
how rotation of the cloud causes the two peaks to shift in wavelength as the
slit is perpendicular to the rotation axis, and how the relative amplitude of
the two peaks is changed. In reality, damped Lya systems are likely to have a
clumpy gas distribution with turbulent velocity fields, which should smooth the
line emission profile, but should still leave the rotation signature of the
wavelength shift across the system.Comment: 19 pages, 17 eps figures. One panel is added in Fig.1 to show the
recoil effect. Revisions are made in response to the referee's comments.
Accepted for publication in Ap
Triple-Pomeron Matrix Model for Dispersive Corrections to Nucleon-Nucleus Total Cross Section
Dispersive corrections to the total cross section for high-energy scattering
from a heavy nucleus are calculated using a matrix model, based on the
triple-Pomeron behavior of diffractive scattering from a single nucleon, for
the cross section operator connecting different states of the projectile
nucleon . Energy-dependent effects due to the decrease in longitudinal momentum
transfers and the opening of more channels with increasing energy are included.
The three leading terms in an expansion in the number of inelastic transitions
are evaluated and compared to exact results for the model in the uniform
nuclear density approximation for the the scattering of nucleons from Pb^{208}
for laboratory momenta ranging from 50 to 200 GeV/c.Comment: 16 pages, 2 figures, RevTex
Lyman alpha line formation in starbursting galaxies II. Extremely Thick, Dustless, and Static HI Media
The Lya line transfer in an extremely thick medium of neutral hydrogen is
investigated by adopting an accelerating scheme in our Monte Carlo code to skip
a large number of core or resonant scatterings. This scheme reduces computing
time significantly with no sacrifice in the accuracy of the results. We applied
this numerical method to the Lya transfer in a static, uniform, dustless, and
plane-parallel medium. Two types of photon sources have been considered, the
midplane source and the uniformly distributed sources. The emergent profiles
show double peaks and absorption trough at the line-center. We compared our
results with the analytic solutions derived by previous researchers, and
confirmed that both solutions are in good agreement with each other. We
investigated the directionality of the emergent Lya photons and found that limb
brightening is observed in slightly thick media while limb darkening appears in
extremely thick media. The behavior of the directionality is noted to follow
that of the Thomson scattered radiation in electron clouds, because both Lya
wing scattering and Thomson scattering share the same Rayleigh scattering phase
function. The mean number of wing scatterings just before escape is in exact
agreement with the prediction of the diffusion approximation. The Lya photons
constituting the inner part of the emergent profiles follow the relationship
derived from the diffusion approximation. We present a brief discussion on the
application of our results to the formation of Lya broad absorption troughs and
P-Cygni type Lya profiles seen in the UV spectra of starburst galaxies.Comment: 24 papges, 12 figures, The revised version submitted to Ap
Steroid-Responsive Encephalopathy Associated with Autoimmune Thyroiditis Presenting as Confusion, Dysphasia, and Myoclonus
Steroid response encephalopathy associated with autoimmune thyroiditis (SREAT), or Hashimoto's encephalopathy, is a rare disorder believed to be immune-mediated. It is most often characterized by a subacute onset of confusion with altered level of consciousness, seizures, and myoclonus. We describe the case of a 48-year-old gentleman who presented with confusion and dysphasia. Specific clinical features and laboratory results led to a diagnosis of Hashimoto's encephalopathy. This case highlights the core features of this condition and the potential for complete response to steroid therapy
Supporting Primary and Secondary Beginning Teachers Online: Key findings of the Education Alumni Support Project
During 2005, the Education Alumni Support Project (EdASP) (Maxwell, Smith, Baxter, Boyd, Harrington, Jenkins, Sargeant & Tamatea 2006) provided online support for University of New England (UNE) graduand, and later, graduate, teachers as they commenced their careers. The project was based on research which reported that many beginning teachers did not get the support they needed as permanent or contract workers, or, as casual, relief or support teachers, and that small scale trials had shown that online support could be effective. One third of beginning teachers who were alumni of UNE in 2004, reported they did not receive adequate or any mentoring. UNE web-based technologies provided the teachers and mentors with online environments for professional and social interaction, and resource sharing. We found that support was especially sought by the project participants in their first school term, and there were differences in the levels of online support sought by secondary and primary beginning teachers. The project raises implications for on-going systemic support for beginning teachers, the issue of transition from students to teachers, as well as questions about teacher education studentsâ preparation. This paper provides the key findings of the project. Detailed description of the project structure, data collection and data analysis are available in Maxwell et al. (2006)
Genesis Mission Bulk Metallic Glass Solar Wind Collector: Characterization of Return Samples Available for Re-Allocation
The Genesis mission collected solar wind atoms for 28 months with a variety of collectors mounted on a spacecraft. A total of fifteen pure materials were selected as collectors based on engineering and science requirements. One of the materials was the bulk metallic glass (BMG). It was intended for collecting noble gases and solar energetic particles (SEP). This material is an amorphous metal which was custom made by C.C. Hays at the California Institute of Technology. The final glass composition is Zr58.5Nb2.8Cu15.6Ni12.8Al10.3 (in atom percent). The BMG was located on top of the wafer array mechanism and was exposed for the entire time the science canister was open (~28 months). Fortunately, the BMG did not suffer any serious damage and was intact after the Genesis canisters hard-landing into the Utah desert (Fig. 1)
Study of a small solar probe /sunblazer/. part ii- spacecraft and payload design progress report, jul. 1, 1964 - jun. 30, 1965
Design considerations for Sunblazer solar probe and payloa
Application of ERTS-1 imagery to state wide land information system in Minnesota
There are no author-identified significant results in this report
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